THEY 2.2

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2.2 Measuring Earthquakes

Vocabulary


focus: points under the Earth's surface where rocks break under a stress force and as a result, causing an earthquake.
epicenter: points on the surface of the Earth that is directly over the focus of the Earth.
seismic waves: a vibration travels through the Earth carrying the energy that was released during when an earthquake striked.
p waves: a seismic wave that compresses the ground as a result it expands the Earth's surface.
s waves: a seismic wave that moves the Earth's surface vertically and horizontally.
surface waves: a different type of seismic wave that occurs when the P waves and S waves reaches the surface of the Earth.
seismograph: a device that records the movements of the ground caused by the seismic waves they travel through the Earth.
magnitude: the measurement of an earthquake strength based on the movements along faults created by the seismic waves.
Mericalli scale: a scale that rates earthquakes according to how much damage they cause by their intensity.
Richter scale: a scale that rates seismic waves as by being measured by a certain type of mechanical seismograph.
moment magnitude scale: a scale that rates earthquakes by estimating the total amount of energy released from the earthquake.

Outline

Seismic Waves

  • seismic waves are vibrations that is carrying energy that was released from the Earth
    • seismic are ripples that travel through Earth's crust
Primary Waves
  • The P Waves are primary waves
    • The P Waves expand in the ground

Secondary Waves
  • After the P Waves the S Waves Come
    • When an earthquake occur, the S Waves vibrate from side to side
Surface Wave
  • After the P and S Waves reach the surface of the earth
    • more slower than the P and S Waves, but creates more critical damage than the P and S Waves

Detecting Seismic Waves

  • for detecting seismic waves geologists use seismographs
    • seismographs measure the movement of an earthquake created by a seimic wave throughout the earth

Measuring Earthquakes

  • there are 20 unique types of measures for rating earthquakes with their own strengths and shortcomings
    • three of the ways of measuring earthquakes are the Mercalli scale, the Richter scale, and moment magnitude scale
The Mercalli Scale
  • this scale records the intensity of an earthquake
    • these measurements are not exact because the intensity rate might change at times
The Ritcher Scale
  • the Richter scale measures the size of the seismic waves
    • the scale might have an exact measurement on short distances, but long distant measurements are incorrect
The Moment Magnitude Scale
  • The Moment Magnitude Scale estimates the total energy that was sent out by an earthquake
    • the moment magnitude scale can measure earthquakes that are small or large and earthquakes that are near or far

Locating the Epicenter

  • geologist draw circles on certain seismograph areas on the radius of each of the following circle is the distance from the seismograph all the way to the epicenter
    • this calculation does not always set where the epicenter really is.